1. Field of the Invention
The present invention relates to a Chinese character input method with limited number of buttons.
2. Prior Art
A conventional Chinese input method converts an input syllable into a Chinese character. In the main land of China, a syllable is input by Pinyin. In Taiwan, a syllable is input by Zhuyin.
Every Chinese character consists of one syllable. For the Pinyin method, one syllable is represented by one through six alphabetic character(s). Therefore, even if a keyboard that has twenty-six buttons corresponding to twenty-six alphabetic characters is used, one through six keystroke(s) is (are) required.
Further, a Chinese syllable consists of an initial corresponding to a consonant part and a final corresponding to a vowel part. An initial consists of a single consonant and a final consists of three parts at the maximum. A semi-vowel (transition vowel) may intervene between an initial and a final. A semi-vowel may belong to the initial by connecting with a consonant (in the specification, a combination of an initial and a semi-vowel is referred to as a “complex initial”), or a semi-vowel may belong to the final. On the other hand, when a consonant follows the vowel in the final, the consonant belongs to the final.
An input method using such a structure of a Chinese syllable has been known. In this method, an operator determines a syllable by one keystroke to specify an initial and one keystroke to specify a final. However, this method requires a keyboard having about thirty buttons for inputting the initial and the final.
The above-described Chinese input methods are designed for a general computer having a full-keyboard. In recent years, a Chinese input method for an information device having about twelve buttons such as a cellular phone and PDA is required. In response to the requirement, various methods have been developed to input a Chinese syllable with the fewest possible number of keystrokes using small numbers of buttons.
For example, a input method used in a cellular phone on the market requires a first keystroke to select an initial group containing a plurality of initials, a second keystroke to select an initial vowel of a final, a third keystroke to select a final (a plurality of finals may be assigned to a button), and fourth and subsequent keystrokes to specify a desirable Chinese character from the candidates that belong to the syllables defined by the selected initials and the selected finals.
However, the input method used in a cellular phone cannot specify a syllable with three keystrokes for all kinds of syllables. In some cases, since the three keystrokes merely extract the syllables as candidates, an operator must specify the target character from many candidates, which complicates the input operation.
U.S. patent application No. 20020193984 discloses the Chinese language input system that enables to specify a syllable with three keystrokes using nine through twelve buttons as the first embodiment. In the first embodiment, a first keystroke selects an initial group, a second keystroke selects the initial and a final group, and a third keystroke selects the final. The publication also discloses the Chinese input method that specifies a syllable with two through four keystrokes as the second embodiment. In the second embodiment, a first keystroke selects a sound group, a second keystroke specifies a syllable that consists of an initial and a simple final (a final having a single vowel), a third keystroke specifies a syllable that consists of an initial and a final without a semi-vowel, and a fourth keystroke specifies a syllable that consists of an initial and a final with a semi-vowel. The input method of the second embodiment can specify a syllable that consists an initial and a simple final with only two keystrokes.
However, the Chinese input method of the first embodiment disclosed in the publication can specify all kinds of syllables with three keystrokes, while it cannot specify any syllables with two keystrokes. On the other hand, the method of the second embodiment of the publication can specify a syllable that consists of an initial and a simple final with two keystrokes, while it requires four keystrokes to specify a syllable that consists of an initial and a final with a semi-vowel.
Further, the final groups are symbolized by different symbols in the first embodiment disclosed in the publication. That is, the simple final is symbolized by “?”, a complex final transcribed with letters without a semi-vowel is symbolized by “*”, a complex final with a semi-vowel “i” is symbolized by “i*”, a complex final with a semi-vowel “u” is symbolized by “u*”, and a complex final with a semi-vowel “v” is symbolized by “v*”. Therefore, a user must understand the meanings of the symbols “?” and “*”.